Eutectic absorbent for efficiently separating hydrogen chloride

Abstract

The invention relates to a eutectic absorbent for efficiently separating and recycling hydrogen chloride, and belongs to the technical field of gas separation and purification. The eutectic absorbent is formed by compounding quaternary ammonium salt and polyhydric alcohol according to a certain proportion, synthesis raw materials are rich and easy to obtain, the synthesis process is simple and easy to operate, and large-scale preparation of the absorbent is safe and reliable. The anion and cation of the quaternary ammonium salt and the hydroxyl of the polyhydric alcohol in the eutectic absorbent can provide a plurality of hydrogen bond acceptors and hydrogen bond donors to facilitate the absorption of hydrogen chloride, the hydrogen chloride can be completely desorbed by adopting a heating or decompression mode, and the regenerated absorbent can be recycled. The absorbent is low in cost, small in viscosity, good in stability and recyclable, is a novel solvent capable of being used for efficient separation and recovery of hydrogen chloride, and has a wide application prospect in separation and recovery of industrial tail gas containing hydrogen chloride.

Description

Technical Field

[0001] The invention belongs to the field of tail gas separation and purification, and in particular relates to a low-melting eutectic absorbent for efficiently separating hydrogen chloride. The absorbent can efficiently separate and recover hydrogen chloride from industrial tail gas. Background Art

[0002] In the petroleum, chemical, pharmaceutical, metallurgical and other industries, there are mixed tail gases containing hydrogen chloride (HCl), such as industrial tail gases emitted during the production of potassium sulfate, PVC, chlorinated hydrocarbons, epichlorohydrin, chlorine and other products. Hydrogen chloride gas has strong corrosiveness and pungent odor, and direct emission is extremely harmful to the environment. At present, trace amounts of HCl in industrial tail gas are directly absorbed by alkali solution to generate chloride salts, resulting in certain solid waste and waste of resources; high-concentration HCl tail gas is mostly produced by water absorption method to produce low-concentration hydrochloric acid. Although this technical solution is simple, the added value of the hydrochloric acid product is low, and the process energy consumption of obtaining pure HCl by hydrochloric acid distillation is high, resulting in low comprehensive economic benefits of HCl recovery by water absorption method.

[0003] In response to the above technical problems, a variety of absorbents for HCl absorption and separation have been reported in the literature, including organic solvents, deep eutectic solvents (DES) and ionic liquids. Organic solvents generally have low boiling points and poor thermal stability; ionic liquids have almost no saturated vapor pressure and good thermal stability, but their viscosity is relatively large. The low eutectic absorbent is a mixture composed of a certain stoichiometric ratio of hydrogen bond acceptors and hydrogen bond donors. Its freezing point is significantly lower than the melting point of the pure substances of each component, and its properties are similar to those of ionic liquid materials. The design and synthesis of new low eutectic absorbents combined with the characteristics of thermal stability, viscosity and gas absorption has great application prospects in the field of gas separation. Li et al. (Sep. Purif. Technol. 2022, 281, 119994) reported that a low eutectic solvent composed of choline chloride and lactic acid, oxalic acid, glycolic acid, glycerol, etc. absorbed about 0.18 to 0.40 g / g of HCl, had good cyclic stability, and the thermal stability of the absorbent was poor; Wu et al. (Sep. Purif. Technol. 2022, 300, 121799) reported that a low eutectic absorbent composed of 1,3-dimethyl-2-imidazolidinone (DMI) and N,N-dimethylurea (DMU), methyl urea (MU), etc. absorbed about 0.60 g / g of HCl, and the thermal decomposition temperature of the absorbent was about 140°C. Patent CN109603437A reports a method for separating and recovering HCl gas using diethylene glycol as an absorbent, wherein the concentration of HCl in the absorbent is 20-40wt% (average absorption capacity is about 0.30g / g), the desorption temperature is 80-150°C, and the desorption rate is about 87%; Patent CN 117339349A reports a method for separating light hydrocarbons and HCl mixed gas by absorbing ethylene glycol, wherein the absorbent is a low-boiling organic solvent, and the solvent consumption in the separation process is relatively large; Patent CN 116550098A reports a method for separating SO2 and HCl mixed acid gas and the application of the method, wherein the absorbent is an organic amine, and a hydrochloride solution is obtained after absorbing HCl, and HCl is released by thermal decomposition, with partial hydrochloric acid as a byproduct. Therefore, it is of great application value to design and develop a low eutectic absorbent with good thermal stability, high absorption capacity and low viscosity to separate and recover HCl.

[0004] The present invention designs a low-melting eutectic absorbent for efficiently separating hydrogen chloride, which can further improve the thermal stability and absorption selection comprehensive performance of the absorbent and recover HCl in industrial tail gas at a low cost. Summary of the invention

[0005] The present invention aims to provide a low-melting eutectic absorbent for efficiently separating hydrogen chloride. The absorbent can efficiently absorb and separate hydrogen chloride from industrial tail gas, and the absorbent has a high HCl absorption capacity and good stability.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a low-melting eutectic absorbent for efficiently separating hydrogen chloride, the absorbent having a hydrogen bond acceptor and a hydrogen bond donor, the absorbent absorbing different concentrations of hydrogen chloride in industrial tail gas under certain conditions, the low-melting eutectic absorbent desorbing hydrogen chloride at a certain temperature and pressure after absorbing hydrogen chloride, the desorbed absorbent can be reused, and the absorbent has good cyclic stability. The absorbent realizes efficient absorption and separation of HCl by forming multi-site hydrogen bonds with HCl.

[0007] The absorbent is prepared by mixing quaternary ammonium salt and polyol in a certain ratio under certain conditions, and the absorbent absorbs and desorbs hydrogen chloride under certain temperature and pressure. The structural formula of the quaternary ammonium salt in the eutectic absorbent is as follows:

[0008]

[0009] Among them, it meets:

[0010] R1, R2, R3, R4 are H or C n H 2n+1 (n is an integer and 0≤n≤10);

[0011] Cl - Br - 、NO3 - 、SO4 - 、ClO4 - ,OTf - At least one of the quaternary ammonium salts.

[0012] The polyol in the eutectic absorbent comprises polyethylene glycol, polypropylene glycol and a general structural formula of C n H 2n+2-x (OH) x One or more polyols of (n, x≥2).

[0013] The molar ratio of the quaternary ammonium salt to the polyol in the low eutectic absorbent is 1: (0.1-10).

[0014] The reaction temperature of the quaternary ammonium salt and the polyol is 0-120°C.

[0015] HCl is absorbed by forming a strong hydrogen bond with the eutectic absorbent, and can be desorbed by heating and / or reducing pressure. Preferably, the absorption temperature of HCl by the absorbent is 10-40°C, and the absorption pressure is 0.1MPa-4.0MPa; the desorption temperature of HCl by the absorbent is 60-120°C, and the desorption pressure is 0.1kPa-1.0MPa, and the desorbed absorbent can be recycled.

[0016] The absorbent can treat industrial tail gas containing hydrogen chloride gas. Preferably, the concentration of hydrogen chloride in the industrial tail gas is 0.1% to 90%.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The low eutectic absorbent provided by the present invention has a higher HCl absorption capacity and better thermal stability than organic solvents and existing DESs; it has lower viscosity and lower synthesis cost than pure ionic liquid absorbents; hydrogen chloride in the absorbent can be quickly desorbed by heating and / or decompression, and the absorbent is easy to regenerate and recycle.

[0019] The following describes the invention in conjunction with specific embodiments. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0021] Example 1

[0022] This embodiment provides an absorbent, and the preparation method of the absorbent is as follows:

[0023] Weigh 0.1 mol (13.62 g) of tetramethylammonium nitrate into a 100 mL flat-bottom conical flask, weigh 0.02 mol (8.00 g) of polyethylene glycol 400 and add it into the flat-bottom conical flask, control the reaction temperature at 70 °C and stir for 6 h to complete the reaction;

[0024] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 40°C and 0.1 MPa. The mass change of the absorption bottle was recorded at regular intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0025] Example 2

[0026] This embodiment provides an absorbent, and the preparation method of the absorbent is as follows:

[0027] Weigh 0.10 mol (6.75 g) of methylamine hydrochloride into a 100 mL flat-bottom conical flask, weigh 0.60 mol (37.24 g) of ethylene glycol and add it into the flat-bottom conical flask, control the reaction temperature at 90 °C and stir for 6 h to complete the reaction;

[0028] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 30°C and 0.1 MPa. The mass change of the absorption bottle was recorded at regular intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0029] Example 3

[0030] This embodiment provides an absorbent, and the preparation method of the absorbent is as follows:

[0031] Weigh 0.02 mol (6.45 g) of tetrabutylammonium bromide into a 100 mL flat-bottom conical flask, weigh 0.10 mol (20.00 g) of polyethylene glycol 200 and add it into the flat-bottom conical flask, control the reaction temperature at 90 °C and stir for 4 h to complete the reaction;

[0032] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 40°C and 0.2 MPa. The mass change of the absorption bottle was recorded at regular intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0033] Example 4

[0034] This embodiment provides an absorbent, and the preparation method of the absorbent is as follows:

[0035] Weigh 0.10 mol (15.17 g) of butyltrimethylammonium chloride into a 100 mL flat-bottom conical flask, weigh 0.20 mol (21.22 g) of diethylene glycol and add it into the flat-bottom conical flask, control the reaction temperature at 40 °C and stir for 4 h to complete the reaction;

[0036] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 10°C and 1.0 MPa. The mass change of the absorption bottle was recorded at regular intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0037] Example 5

[0038] Weigh 0.10 mol (20.78 g) of octyltrimethylammonium chloride into a 100 mL flat-bottom conical flask, weigh 0.10 mol (10.61 g) of diethylene glycol and 0.10 mol (15.02 g) of triethylene glycol and add them into the flat-bottom conical flask at the same time, control the reaction temperature at 40 ° C, stir for 4 hours and the reaction is completed;

[0039] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 30°C and 3.0 MPa. The mass change of the absorption bottle was recorded at regular intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0040] Example 6

[0041] Weigh 0.05 mol (8.28 g) of tetraethylammonium chloride and 0.05 mol (16.12 g) of tetrabutylammonium bromide into a 250 mL flat-bottom conical flask, weigh 0.50 mol (31.04 g) of ethylene glycol and 0.50 mol (100.00 g) of polyethylene glycol 200, respectively, and add them into the flat-bottom conical flask at the same time. Control the reaction temperature at 40 ° C and stir for 4 hours to complete the reaction;

[0042] 2.00 g of the above-mentioned eutectic absorbent was added to an absorption bottle with a volume of 10 mL. Pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 30°C and 4.0 MPa. The mass change of the absorption bottle was recorded at intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0043] Example 7

[0044] The absorbent provided in Example 4 was subjected to a cyclic absorption-desorption test, specifically: 5.00 g of absorbent was added to an absorption bottle with a volume of 20 mL, HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 30°C and 0.1 MPa, and the mass change of the absorption bottle was recorded at intervals until the absorption reached equilibrium. The saturated absorbent was desorbed by heating and reducing pressure (under the conditions of 60°C and 30 kPa), and the results of the absorption-desorption cycle experiment were performed for 5 consecutive times. The performance of the absorbent provided in this example is stable as shown in Table 1.

[0045] Table 1 Absorption-desorption cycle stability test of absorbent for hydrogen chloride gas

[0046]

[0047] It can be seen from Table 1 that the absorbent of the present invention has good absorption stability for hydrogen chloride for 5 cycles and good regeneration performance.

[0048] Comparative Example 1

[0049] This comparative example provides an absorbent, specifically EG: ethylene glycol.

[0050] Comparative Example 2

[0051] This comparative example provides an absorbent, specifically DEG: diethylene glycol.

[0052] Comparative Example 3

[0053] This comparative example provides an absorbent, specifically ChCl-EG (1:2): choline chloride and ethylene glycol.

[0054] The absorption effect of the absorbents provided in Comparative Examples 1-3 on hydrogen chloride gas was tested respectively by the following method: 2.00 g of absorbent was added to an absorption bottle with a volume of 10 mL, pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle under the conditions of 30° C. and 0.1 MPa, and the mass change of the absorption bottle was recorded at intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating-decompression.

[0055] Table 2 shows the test results of the absorption effect of the absorbents provided by Examples 1-7 on hydrogen chloride gas and the test results of the absorption effect of the absorbents provided by Comparative Examples 1-3 on hydrogen chloride gas.

[0056] The following points can be drawn from Table 2: Compared with the absorbents provided in Comparative Examples 1-3, the absorbents provided in Examples 1-6 of the present invention can achieve efficient absorption and separation of hydrogen chloride gas.

[0057] Table 2 Test results of absorbent for hydrogen chloride gas absorption effect

[0058]

[0059] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A eutectic absorbent for efficient separation of hydrogen chloride, characterized in that: The low eutectic absorbent is compounded with quaternary ammonium salt and polyol in a certain ratio under certain conditions; the absorbent can absorb / desorb hydrogen chloride at a certain temperature and pressure, and can efficiently absorb and separate hydrogen chloride of different concentrations in industrial tail gas.

2. The quaternary ammonium salt structural formula in the eutectic absorbent according to claim 1 is: in, R1, R2, R3, R4 are H or C n H 2n+1 (n is an integer and 0≤n≤10); Cl - Br - 、NO3 - 、SO4 - 、ClO4 - ,OTf - At least one of the quaternary ammonium salts. Wherein, the quaternary ammonium salt is a composite of one or more.

3. The polyol in the eutectic absorbent according to claim 1 comprises polyethylene glycol, polypropylene glycol and a general structural formula of C n H 2n+2-x (OH) x One or more polyols of (n, x≥2).

4. The low eutectic absorbent according to claim 1, wherein the quaternary ammonium salt and the polyol are in a certain molar ratio, wherein the molar ratio of the quaternary ammonium salt to the polyol is 1:(0.1-10).

5. The eutectic absorbent according to claim 1 is compounded under certain conditions, characterized in that: The compounding temperature is 0-120°C.

6. The absorption and desorption conditions according to claim 1, characterized in that: The eutectic absorbent has an absorption temperature of 10 to 40° C. and an absorption pressure of 0.1 MPa to 4.0 MPa for the tail gas containing hydrogen chloride; The desorption temperature of the absorbent for hydrogen chloride is 60-120° C., and the desorption pressure is 0.1 kPa-1.0 MPa.

7. The industrial tail gas with different concentrations of hydrogen chloride according to claim 1, wherein the concentration of hydrogen chloride is 0.1% to 90%.

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